Continuous copper refining



Aug. 7, 1956 J. F. JORDAN 2,758,022

- CONTINUOUS COPPER REFINING Filed May 20, 1953 2 Sheets-Sheet 1MOLTEN,IMPURE COPPER SULPHIDE MOLTEN, IMPURE COUNTERCURRENT MOL'I'ENPURE COPPER REACTOR COPPER MOLTEN, PURIFIED COPPER SULPHIDE soCONTiNUOUS -OXYGEN(AIR) CONVERTER MOLTEN, SULPHUR SATURATED COPPE soCONTINUOUS -4---OXYGEN (AIR) CONVERTER MOLTEN,OXYGEN- COPPER OXIDE ORSATURATED COPPER CO, CO INCANDESCENT COLUMN CHARCOAL.

' OF CHARCOAL PORTION MOLTEN, DEOXIDIZED CASTING MOLD(S) INGOTS OF PURECOPPER IN V EN TOR:

{W M ZOO Aug. 7, 1956 2 Sheets-Sheet 2 Filed May 20, 1955 N OE 5:54am5&8 SEEP. 2230:

United States Patent CONTINUOUS COPPER REFINING James Fernando Jordan,Huntington Park, Califl, assignor of one-third to the estate of JamesJordan, deceased Application May 20, 1953, Serial No. 356,197

Claims. (Cl. 75-76) My invention relates to metallurgy wherein coppersulphide is to be converted into copper.

Pyrometallurgical methods never having shown an ability to refine copperto electrical standards, presentday refining procedures consist of acombination of pyrometallurgical methods and the electrolytic process.Such combinations, while yielding the desired purity, do so at theexpenditure of large amounts of capital and at high cost, for theoverall operation is metallurgically awkward. When the cost of producingthe common metals is high, whether for metallurgical or other reasons,all business suffers. The cost of producing copper is high, and it isclear that a correction of this must be found in the metallurgical phaseof the industry, for there is small chance that any dramatic improvementwill be made in the present-day mining and concentration procedures.

I have found a pyrometallurgical refining procedure that yields copperof electrical purity without the electrolytic step.

Practically-all copper smelters arrive at a pool of molten white metalat some stage of their operations, either as a result of melting aniron-free, sulphide ore or concentrate or as the result of a convertingoperation wherein air has been employed to oxidize the iron sulphidecontent of a molten matte. It is at this white metal stage that myprocess begins.

In the usual case, the pool of molten white metal contains, in additionto the gold and silver, objectionable amounts of iron, arsenic,antimony, lead, selenium/tellurium and nickel. I removesubstantially-all of the gold and silver from the white metal, and lowereach of the listed objectionable metals to below about 0.002%, bytreating said molten white metal with the reagent, copper. This I do bycontacting a small stream of white metal with a countercurrent stream ofmolten copper.

While the old bottoms process never showed an ability to produce a metalthat met the critical conductivity test, I have found that the bottomsreactions will yield the required purity if my critical steps areemployed in carrying out said reactions. In generaL'these critical stepsinvolve: (l) a countercurrent flow of the reactants, and (2) themaintenance of something approaching equilibrium between the reactantsall along the contact therebetween. While there are few problemsinvolved in entertaining a contra-flow of molten copper and molten whitemetal, the second critical factor'requires the most carefulconsideration respecting the design of the vessel wherein the contact ismaintained and the most careful operating procedure.

The countercurrent refining vessel disclosed in my patent, U. S. No.2,572,489, is highly suited for treating a molten white metal withmolten copper. 2,572,489 should be consulted for details regarding thisrefining vessel, the shelf arrangement shown in Figures 4 and 5 of saidpatent being particularly recommended. It will be understood that thewaste slag of Figure 1 in 2,572,- 489 is the refined white metal of thepresent invention.

While the molten white metal being passed to my first refining step willordinarily come from a converter or from a holding vessel into whichwhite metal from converters is poured until needed, the molten copperemployed as the refining agent will ordinarily come from a later step inthe process. I recommend that both the white metal and the refiningcopper be at about 1200 C. when they are brought into countercurrentcontact, however, slightly lower or much higher temperatures may beemployed.

The removal of elements such as iron, arsenic, antimony and nickel fromthe white metal by the copper involves simple reduction reactions, whilethe removal of elements such as selenium and tellurium involvesextraction processes. It has been observed that the amount of copperrequired to refine a given white metal depends upon the extractionprocesses rather than the reduction processes. The amount or" copperrequired to extract the selenium and/or tellurium from a given whitemetal depends upon the distribution coelficient of copper selenidebetween the molten white metal and the molten copper at the copper-exitend of the refining process. The most important factor in thisdistribution coefficient seems to be the purity of the copper, and thispurity depends of course on the purity of the molten white metal. It hasbeen observed that, in any given case, the amount of copper required, isinversely proportional to the distribution coefiicient of copperselenide at said copper-exit end of the extraction process, and it hasobserved that, if the selenium is being removed from the molten whitemetal, elements such as iron, arsenic, antimony, nickel, silver and goldare being removed also.

The desired white metal purity is only achieved when the molten whitemetal has been brought into substantial equilibrium with a molten copperthat is essentially-free from all of these impurities, silver and goldbeing exceptions to this rule. This is a critical point, a pointoverlooked by the Welsh and bottoms processes. As mentioned, silver andgold seem to be exceptions to this rule, for a copper reagent containingsilver and gold still exhibits an excellent ability to removeessentially all silver and gold from a molten white metal. As anillustration of the results obtained from gaining equilibrium between animpure white metal and a pure copper reagent: in one test that I carriedout on a white metal containing 0.09% As, 0.11% Sb, 0.05% Fe, 0.02% Ni,11.5 oz/ton Ag and 2.1 oz/ton Au, brought into substantial equilibriumwith a copper of electrical purity, I obtained a white metal containingonly traces of silver and gold, 0.0004% As, 0.0010% Sb, 0.00l5% Fe and0.002% Ni. The amount, of copper employed in this test was 5% of thewhite metal, by weight.

In view of the fact that the molten white metal and molten copper beingfed to this process will ordinarily vary little insofar as the impuritylevels are concerned, seeking and establishing the optimum refining rateand relative rates of reactant flow into the process is simple. With themolten white metal flowing thru the refining vessel at a selected rateand in flowing contact with a stream of molten copper, so that theoverall process is not producing white metal of the desired purity, therate of flow of copper into the process is increased in steps until thedesired purity is obtained in the white metal product, or, alternately,the rate of flow of the raw white metal into the process is decreased insteps until the desired white metal purity is being obtained, or both.When the desired white metal product is being obtained, the flow ofcopper into the process should be increased by some preselected amount,so as to afiord protection against the variables which are inherent withsuch a process.

The copper extraction yields a pure molten White metal and an impurecopper. The impure copper is best cast into anodes and purifiedelectrolytically, thereby recovering the valuable impuritiesconcentrated therein. The pure white metal is flowed to the next step ofmy process, the desulphurizing step.

Desulphurization The next step of my process involves the continuousconversion of the molten, pure white metal into a sulphur-saturatedcopper metal. This I carry out within a refractory-lined refining troughinto which I permit the pure white metal from the extraction process toflow, the conversion being carried out by means of a series of air jetswhich are spread out along said trough so that said jets impinge intothe molten copper sulphide, preferably from a position that lies abovethe surface of the stream of molten sulphide within said trough. Themolten, sulphur-saturated copper arising from the reaction between thecopper sulphide and the oxygen accumulates as a stream that flows alongunderneath the molten copper sulphide, said sulphur-saturated copperleaving said molten copper sulphide by underfiowing a dam positionedacross the trough downstream from the position whereat the moltensulphide is entering said trough. Figure 2 pictures this first stage ofmy desulphurizing process.

Air may be employed in the jets of the first stage of my desulphurizingstep if the mass of sulphide/copper is sufficiently large and if thetrough is well insulated, however, I prefer to use oxygen or airenriched with oxygen, due to the increased refining capacity achievedthereby and due to the favorable temperature build-up that accompaniesthe substitution of oxygen for nitrogen.

The sulphur-saturated copper from my first desulphurizing phase flowsimmediately into the second, final desulphurizing phase wherein thesulphr content of the metal stream is substantially eliminated bysaturating said metal stream with oxygen, said saturation with oxygenbeing achieved by means of a series of impinging air jets. Figure 2shows a combination of the first and second phases of my desulphurizingstep in one refining vessel. The two phases of the desulphurization stepmay be carried out in two separate troughs, if desired.

As the molten, sulphur-bearing copper metal flows along under theimpinging air jets, the sulphur content of the metal stream rapidlyfalls. In view of the fact that the end point of this desulphurizationis diflicult to detect without taking samples of the flowing stream-aprocedure that is not practical in a continous-flow process, I prefer tooperate this second phase so that a substantial amount of copper oxideseparates as a separate phase to float on the molten copper atthemetal-exit end of the second phase of this desulphurizing step. Theformation of this separate, copper oxide phase assures the completion ofthe desulphurizing step, for it indicates that the metal is saturatedwith oxygen. This separate, copper oxide phase may be passed with theoxygen-saturated copper to the next, deoxidizing step, or itmay beblocked from leaving the vessel with the oxygen-saturated copper, thuscausing the molten copper oxide to flow back over sulphur-bearing copperwithin the second desulphurizlng step.

The separate, copper oxide phase formed in this second phase willcontain a portion of the impurities left in the metal after the copperextraction step. Such impurities will of course reenter the metal unlesssteps are taken to separate the separate, copper oxide phase from theoxygen-saturated metal. Generally speaking, the amount of suchimpurities will be very small if the copper extraction step was properlycarried out, however, if desired, such impurities as may be held in theseparate, copper oxide phase may be removed by simply skimming off thefloating copper oxide phase, either within the vessel or after the metalplus molten oxide have left said vessel. If the separate, copper oxidephase is to be carry out the operation after the immiscible liquids haveleft the vessel. A simple underflow/ overflow dam arrangement may beemployed to accomplish this.

Deoxidation The metal leaving the second phase of my desulphurizing stepis saturated with oxygen. As the next step in my process, I removeessentially all of said oxygen from said metal by reacting said oxygenwith incandescent charcoal, by flowing the oxygen-bearing copper thru acolumn of said charcoal, much in the manner that OFHC copper isproduced. I prefer to maintain the charcoal column at temperature bymeans of the molten copper flowing therethru, by operating thedesulphurizing steps so that the molten copper entering the deoxidizingunit contains sufiicient heat to maintain the charcoal column attemperature. This I do by enriching the air employed in thedesulphurizing step sufiiciently with oxygen to yield the requiredtemperature build-up.

The deoxidizing step of my process always produces an oxygen-freecopper, whether the final product is to be an oxygen-free copper or atough-pitch copper.

Casting The preferred embodiment of my process involves the continuouscasting of the fully-deoxidized copper leaving the deoxidizing step. Bycontinuous casting, I mean in a water-jacket mold such as isconventional in the continuous casting art, not a continuous series ofingots or castings. The metal requirements of a continuous casting moldare admirably met by the continuous flow of deoxidized copper from myprocess. Of course, if desired, the metal of my process may be fed toone of the casting machines conventional to the copper refinery. If itis desired to form tough-pitch copper, then the deoxidized copper frommy process should be flowed along a refractory trough under acirculating, controlled flow of an oxidizing gas; for, at a giventemperature, the oxygen pick-up by the flowing metal stream will vary asthe interval of contact. Another simple method of lifting the oxygencontent of the copper to tough-pitch levels involves feeding copperoxide into a flowing copper stream, the rate of feed being in accordancewith the rate of copper flow. Copper oxide for this purpose may beobtained from the second phase of the desulphurizing step, preferably bycooling the oxide, crushing it to a powder and then feeding it into thecopper stream with a reagent feeder.

Figure 1 pictures the flow pattern of my process.

The refractories employable in the various refining vessels of myprocess are those conventional in the present art. While therefractories in contact with the mo]- ten liquids of my process may bethe same as those in contact with the same liquids within conventionalprocedures, it is important to remember that the small amount of suchliquids in action, at any given moment, makes the use of insulationnecessary. Such insulation, and the judicious use of oxygen in place ofall or part of the refining air, makes feasible the maintenance of therequired temperature levels in the flowing streams of my process.

In any given continuous-flow process, such as this, the trick is toarrange the reaction sequence so that the controls lie within theprocess itself, for only then is it possible to envision automaticcontrol. It is not practical to employ thecontrol laboratory in acontinuous-flow process in the same manner that such a laboratory isemployed in the batch-type processes. My present invention admirablymeets all control problems. In the first, copper extraction step, therequired automatic control is gained by employing an excess of thereagent, copper, over that required to remove the average impurities,and this excess may be related to the maximum expectancy with respect tothe swing of the impurities over this norm. Control in the first phaseof the desulphurizing step is fully automatic, for the copper flows outof the phase as soon as it is formed, and control over the second phaseis also automatic, once the oxygen input has been regulated to the endthat a substantial excess of copper oxide is being produced at themetal-exit end of said second phase. All that is needed in this secondphase is an occasional check to assure that the process is continuing toproduce substantial amounts of copper oxide. The final, deoxidizing stepis fully automatic in that the molten copper is brought into contactwith much more carbon than that required to attain the desired degree ofdeoxidation.

The reagent in the air jets of my process is always oxygen. Such oxygenmay be derived from air, oxygen gas or air enriched with oxygen gas. Itherefore employ the term, oxygen, to refer to air, oxygen gas or airenriched with oxygen gas throughout my claims.

I claim as my invention:

1. The method of converting a stream of molten white metal into a streamof essentially sulphur-free, oxygensaturated, molten copper, whichcomprises: pouring said molten white metal into one end of an elongatedreaction zone to form a stream of molten white metal within saidreaction zone; directing a series of oxygen jets into reacting contactwith and along said flowing white metal stream Within said reaction zoneto form molten copper that settles through said molten white metalstream to form a stream of sulphur-saturated, molten copper upon of anelongated refining zone while blocking the flow of said molten whitemetal thereinto; directing a series of oxygen jets into reacting contactwith and along said sulphur-saturated, molten copper stream within saidrefining zone as said copper stream flows through said refining zone,sufiicient oxygen being fed into reacting contact with said copperstream within said refining zone by means of said oxygen jets to form aseparated layer of molten copper oxide floating on said copper streamwithin said refining zone; and thereupon flowing said copper stream outof said refining zone.

2. The method according to claim 1 in which said layer of molten copperoxide separates from said copper stream near the copper exit end of saidelongated refining zone.

3. The method according to claim 1 in which said molten white metal isrefined before being poured into said reaction zone by contacting andreacting said molten white metal with an essentially pure, molten coppersolvent, said solvent being separated from the refined molten Whitemetal before said white metal is poured into said reaction zone.

4. The process according to claim 1 in which said molten, separatedcopper oxide is flowed back over said stream of sulphur-saturatedcopper.

5. The process according to claim 1 in which said molten, separatedcopper oxide flows into a deoxidizing process with the oxygen-saturatedcopper.

6. The process according to claim 1 in which the oxygen-saturated copperis flowed through and in intimate contact with a loosely-packed columnof incandescent charcoal until said copper is essentially deoxidized.

7. The process according to claim 6 in which said oxygen-saturatedcopper is accompanied by a molten slag consisting of copper oxide.

8. The process according to claim 6 in which said deoxidized copper isflowed into a continuous, water-jacket mold.

9. The process according to claim 6 in which said deoxidized copper ispoured into a series of individual molds.

10. The process according to claim 9 in which oxygen is added to saiddeoxidized copper before said copper is poured into said molds.

References Cited in the file of this patent UNITED STATES PATENTS1,175,266 Hybinette Mar. 14, 1916 1,966,376 Cavers et al July 10, 19342,109,272 Larson et al Feb. 22, 1938 2,572,489 Jordan Oct. 23, 1951FOREIGN PATENTS 698,758 Great Britain Oct. 21, 1953

1. THE METHOD OF CONVERTING A STREAM OF MOLTEN WHITE METAL INTO A STREAMOF ESSENTIALLY SULPHUR-FREE, OXYGENSATURATED, MOLTEN COPPER, WHICHCOMPRISES: POURING SAID MOLTEN WHITE METAL INTO ONE END OF AN ELONGATEDREACTION ZONE TO FORM A STREAM OF MOLTEN WHITE METAL WITHIN SAIDREACTION ZONE; DIRECTING A SERIES OF OXYGEN JETS INTO REACTING CONTACTWITH AND ALONG SAID FLOWING WHITE METAL STREAM WITHIN SAID REACTION ZONETO FORM MOLTEN COPPER THE SETTLES THROUGH SAID MOLTEN WHITE METAL STREAMTO FORM A STREAM OF SULPHUR-SATURATED, MOLTEN COPPER UPON WHICH SAIDMOLTEN WHITE METAL STREAM IS FLOATING; FLOWING SAID SULPHUR-SATURATED,MOLTEN COPPER STREAM INTO ONE END OF AN ELONGATED REFINING ZONE WHILEBLOCKING THE FLOW OF SAID MOLTEN WHITE METAL THEREINTO; DIRECTING ASERIES OF OXYGEN JETS INTO REACTING CONTACT WITH AND ALONG SAIDSULPHUR-SATURATED, MOLTEN COPPER STREAM WITHIN SAID REFINING ZONE ASSAID COPPER STREAM FLOWS THROUGH SAID REFINING ZONE, SUFFICIENT OXYGENBEING FED INTO REACTING CONTACT WITH SAID COPPER STREAM WITHIN SAIDREFINING ZONE BY MEANS OF SAID OXYGEN JETS TO FORM A SEPARATED LAYER OFMOLTEN COPPER OXIDE FLOATING ON SAID COPPER STREAM WITHIN SAID REFININGZONE; AND THEREUPON FLOWING SAID COPPER STREAM OUT OF SAID REFININGZONE.